Apparatus for determining the solidifying temperatures of vapors dispersed in gases



April 1, 1952 f -rm 2,591,084

APPARATUS FOR DETERMINING THE SOLIDIFYING TEMPERATURES OF vAPoRs DISPERSED IN GASES Filed Sept. 50, 1948 ARMOR B. MAR IN NVENTOR TJ/ZWL a. figw ATTORNEY Patented Apr. 1, 1952 APPARATUS FOR DETERMINING THE S OLID IF YIN G TEMPERATURES OF VAPORS DISPERSED IN GASES Armor B. Martin, Butte, Mont.

Application September 30, 1948, Serial No. 51,968

6 Claims.

This invention relates to apparatus for continuously ascertaining and, if desired, recording the temperature at which solids are deposited from a gas stream containing solidifiable vapors.

In the transportation or processing of natural gas, which often or usually contains water vapor,

much trouble is often experienced by reason of the deposition of hydrocarbon hydrates in pipe lines or apparatus which may be subjected, to even moderately low temperatures. This difficulty may be avoided by bringing the water content of the gas to a suificiently low level, but dehydrating operations are expensive and the cost increases rapidly as the permissible water content of the gas is lowered.

Further, and of even more importance, the temperature at which solids begin to be deposited from a gas stream may fluctuate, by reason either of changes in the composition of the gas or of unavoidable variations in the functioning of the dehydrating unit, and thus a low-temperature pipe line or piece of apparatus may without Warning be supplied with gas capable of choking it with solids at the prevailing temperature.

The primary purpose of the apparatus herein described is to give warning of the approach of solid-depositing conditions and thus to permit correction of the undesired condition before actual choking occurs.

A further purpose of the invention is to permit the dehydrating operation to be so regulated as to maintain the gas stream at a safe but only a slight distance below the water content at which choking would occur at the minimum temperature to which the gas stream will be subjected. The application of excess dehydrating effect is thus made unnecessary and the desired object, of ensuring against deposition of solids, is attained at a'reduced cost.

The apparatus hereinafter described comprises as essential elements: means for passing a stream of the gas through an elongated and very narrow channel; means for applying a cooling effect to the wall of the channel, and means for observing the temperature of the channel at the moment at which it begins to be obstructed by the accumulation of solids on its wall. These elements alone suffice for making individual determinations of solidifying temperature, but in order to produce continuous and automatic operation of the device it is further provided with means for withdrawing the cooling effect when, the channel becomes obstructed, for warming the channel to causethe removal of the obstructing solids, for again applying the cooling effect as soon as the 2. channel is again free from obstruction, and for continuously recording the temperature of the channel. I

Referring to the attached drawing, illustrating a preferred form of the device, partly in section and partly in elevation: a tube I0 connects a gas pipe line, not shown, with a T fitting I I which drains into a receiver I2. The purpose of this receiver is to trap out suspensoids which may be carried in the test stream and to accumulate any liquids which may condense on the wall of tube I5, later described, and which would interfere with accurate readings if not removed.

The T fitting carries an upwardly extending tube I3 which terminates in a cross fitting I 4. The upper end of the cross fitting has a socket into which is fitted a tube l5 and a larger socket supporting a surrounding and concentrically arranged tube I6, the upper end of the latter being closed as by a plate IT. The flow of gas through this structure is as indicated by the directional arrows: from tube I0 upwardly through tubes I3 and I5 until the gas encounters plate I1, then downwardly through the annular channel I8 between tubes I5 and I6, and outwardly through a side tube I9 to the atmosphere or other point of disposition at low pressure. I

The side tube is provided with an orifice plate 20 having a fixed orifice 2| therein, the size of this orifice being so proportioned to the crosssectional area of annulus I8 that the flow through it produces a pressure difference between the two ends of the annulus of a low order, for example from 1 pound to 5 pounds gauge, when the assembly is passing a small stream of gas, as for example 20 cubic feet per hour. As the static pressure in tubes I3 and I5 may be high, an uncontrolled orifice to pass so small a stream of gas may be too minute to function dependably, and it is desirable to insert a control. valve of some sort in tube I 9 downstream from the orifice. A manual valve may be used but it is preferable to use a diaphragm-controlled valve as indicated at 55, thus maintaining a constant back pressure against the orifice and permitting a larger orifice to be used The exterior of tube I 5 and the interior of tube It should be of uniform diameter from end to end and should be smooth, and these smooth surfaces should be concentric: The width of annulus I8 is much exaggerated in the drawing. For the maximum degree of. sensitivity the annulus should be very narrow, as for example from 0.005 inch to as little as 0.001 inch. The wider the annulus the slower will be the response of the instrument and the greater the difference between the temperature at which the channel becomes obstructed and the temperature at which the obstruction is removed. It may be necessary, however, to use a relatively wide annulus in reading the frosting points produced by solids such as water ice, which are removed by fusion rather than by sublimation, in order to minimize the effects of capillarity.

The concentric tubes are housed in a liquidtight jacket 22 which is approximately filled with a heat conductive liquid having a low freezing point, for example a strong brine, metallic mercury or the like. A tube 24 provided with a needle valve 25 connects inlet tube ill (in this instance by way of receiver I2) with the lower end of the jacket, permitting a small stream of the warm gas to bubble up through liquid bath 23, keeping it in agitation and also imparting heat to the bath to accelerate removal of the solid deposit by fusion or vaporization when the cooling effect is withdrawn. This gas escapes through tube 28 to the atmosphere, directly or through vent tube 19.

A thermometer 21 is passed through the jacket wall into the liquid bath and its indications may 'be read directly but preferably are recorded by any type -of continuous temperature recorder, suggested at 28.

A cooling coil 29 of suitable metallic tubing is placed around tube I S, the terminals 3| and 32 of this coil being sealed into the jacket wall. The inlet end of this coil is provided with an expansionvalve or orifice 33; the outlet end 32 is provided with a solenoid-actuated valve 3%. The latter 'is arranged to be responsive to variations in pressure difference between the two ends of annulus F8 in the following manner.

A mercury manometer 35 has one of its ends in communication with gas inlet tube l0 through atube 36, the other end being in communication with {the discharge end of annulus l8 through tube 31. Themanometer thus indicates, in inches or millimetres of mercury, the momentary pressure difference between the ends of annulus It.

An electrical contact'point 3B is sealed into the leftha'ndleg of the manometer at'such level that it'isincontact with themercury-at all times, and a second electrical contact point 39 is projected through a bushing 40 to apoint slightly above the le'velof mercury-when thech'annel is unobstructed'and th'e pressure diif'erence at the minimum. Leads 41,42 and 43 connect these two points with the solenoid coil 44 and with a source of power, the solenoid and its connections being so arranged that valve 34 is closed when the'electrical circuit is completed by'the elevation of mercury level due to increased pressure drop across the annulus, and opened when this circuit is broken.

The cooling coil 29 is supplied with a refrigerating jfiuid, as for example liquefied anhydrous ammonia, sulfur dioxide-or one of the'chlorofluoromethanes. Lacking an existing supply of refrigerant, it may be provided by a small independent system including a compressor 45 driven by an'electric motor 46. A conduit 41 connects the intake of the compressor with valve 34; the compressor discharge passes through acondensing coil 48 to a'surge tank 49 from which the liquid refrigerant passes through conduit 50 to expansion valve 33'by which it is admitted to the coil to evaporate therein and produce rapid cooling of the liquid bath and of the wall of the channel.

So long'as solenoid valve 34 is open the flow of 're'frigerantcontinues and the temperature of the bath decreases, finally reaching the point at which solids begin to collect on the inner wall of tube IS. The flow through annulus I8 is thus obstructed, the pressure difference between the two ends of the annulus increases, the mercury column in manometer 35 rises, completing the electrical circuit, and valve 34 closes. The flow of refrigerant into coil 29 ceases almost instantly, interrupting the cooling effect, and atmospheric heat plus heat imparted by the gas stream introduced into the bath through tube 24 rapidly raises the temperature of the bath to the point at which the solids melt or vaporize and the obstruction to flow through the annulus is removed. The temperature fluctuation during this cycle, appearing as a sinusoidal curve on the recorder chart, is a function of the sensitiveness of the instrument. It need not exceed about 2 Fahrenheit and may be even less. 7

The sensitiveness of the instrument may be increased by placing refrigerating coil 29 in metallic contact with the outer Wall of tube l6 and providing a heat-conductive bond of copper, solder or the like between the two metallic elements. When this modification is made the liquid bath 23 is no longer functional for transferring heat between the coil and the annulus wall and may be omitted. The Jacket 22, if retained, then becomes simply a means for directing a stream of warming gas over the coil.

Further, if the instrument is to be used for determining the temperature of deposition of hydrocarbon hydrates or other solids which vaporize without passing through the liquid phase, the two tubes which produce annulus It! may be substituted by a capillary tube, for example of stainless steel, wound in contact with refrigerating coil 29 and heat-conductively bonded to it.

As it is undesirable to allow the compressor to continue to operate after it is unloaded by the closing of the valve in its intake, a cut-out for the motor may be provided. This may take the form of a switch 5| in one of the power leads 52 or 53 to motor 46, this switch being actuated by a diaphragm and chamber 54 communicating with intake conduit 47 and so connected as to open the switch and inactivate the motor when the intake pressure falls below a predetermined level.

The details of apparatus above described'are in greater part intended to be suggestive only and numerous modifications of the structure may be made without loss of functionality or departure from the spirit of the invention.

For example, a housed Sylphon bellows or a diaphragm pressure regulator maybe interposed between conduits 36 and 31 and arranged to open and close valve 34 in response to changes in .the pressure difference between the ends of the annulus. Valve 34 may beplaced in either end of coil 29,. The requirement for compressor 45 and :its accessories will be avoidedif a supply of liquefied ammonia or other gaseous refrigerant is otherwise available.

While the device is described as applied'to the observation of gases capable of depositing hydrocarbon hydrates, it is equally adapted for use with other gases which deposit solids on cooling.

Examples are artificial fuel gases containing naphthalene vapor, gases containing iodine,'waxy hydrocarbons or carbon dioxide, and air containing water vapor. The term solids is used in the appended claims to cover any-solidrsubstance which may be deposited on a sufliciently cooled surface over which a gas stream containing the vapor of the substance is passed.

I claim as my invention:

1. Apparatus for determining the temperature at which a solid is deposited from a gas containing the vapor of said solid, comprising: a channel of area suiliciently restricted that its resistance to gas flow is measurably increased by minute deposits of solids therein; means for passing a stream of said gas through said channel; means for progressively cooling said channel while said stream is flowing therethrough; means arranged to indicate continuously the difference in pressure between the ends of said channel, and means for observing the temperature of said channel at the moment at which said indicating means shows an increase in said pressure difierence.

2. Apparatus for determining the temperature at which a solid is deposited from a gas containing the vapor of said solid, comprising: a channel of area sufficiently restricted that it resistance to gas flow is measurably increased by'minute deposits of solids therein; means for passing a stream of said gas through said channel; means for applying a cooling efiect to said channel while said stream is flowing therethrough to progressively reduce the temperature of said channel to the point at which said vapors are congealed and deposited therein; automatic means responsive to fluctuations in pressure difference between the ends of said channel for withdrawing said cooling effect when said channel becomes obstructed by the deposition of solid therein and for reapplying said cooling effect when said ohstruction is removed by elevation of the temperature of said channel, and means for continuously recording the temperature of said channel.

3. Apparatus for determining the temperature at which a solid is deposited from a gas containing the vapor of said solid, comprising: a channel of area so restricted that its resistance to gas flow is measurably increased by minute deposits of solids therein, said channel having a metallic wall; means for passing a stream of gas through said channel; means operating while said gas stream is flowing for passing a flow of refrigerating fluid in heat-conductive relation to said wall, to gradually cool said wall to a temperature at which solids are deposited thereon; means responsive to fluctuations in pressure difierence between the ends of said channel for interrupting the flow of refrigerating fluid when said channel becomes obstructed by the deposition of solids on said wall and for causing resumption of said flow when said obstruction disappears, and means for continuously observing the temperature of said wall.

4. Apparatus for determining the temperature at which a solid is deposited from a gas containing the vapor of said solid, comprising: a metallic conduit so restricted in cross-sectional area that its resistance to gas flow is measurably increased by minute deposits of solids therein; means for passing a stream of said gas through said conduit; a second metallic conduit disposed in heatconductive relation with first said conduit; means operating while said gas stream is flowing for passing a flow of refrigerating fluid through said second conduit to reduce the temperature of vapors; means responsive to fluctuations in pressure difierence between the ends of first said conduit for interrupting the flow of said refri'gerating fluid when first said conduit becomes obstructed by the deposition of solids therein and for causing resumption of said flow when said obstruction disappears, and means for continuously observing the temperature of the Wall of said conduit.

5. Apparatus for determining the temperature at which a solid is deposited from a gas containing the vapor of said solid, comprising: walls defining an annular channel of such restricted width that its resistance to gas flow is measurably increased by minute deposits of solids therein; means for passing a stream of said gas through said channel; mean operating while gas is flowing through said channel for applying a cooling efiect to one of said walls to lower the temperature thereof to the point at which solids are congealed and deposited thereon from said gas; means responsive to fluctuations in pressure difference between the ends of said channel for withdrawing said cooling efiect when said channel becomes obstructed by said deposition of solids and for reapplying said cooling effect when said obstruction is removed by elevation of the temperature of said walls, and means for continuously observing the temperature of the wall to which said cooling effect is applied.

6. Apparatus for determining the temperature at which a solid is deposited from a gas containing the vapor of said solid, comprising: concentric tubes forming an annular channel of such restricted width that its resistance to gas flow is measurably increased by minute deposits of solids therein, the outer of said tubes being immersed in a heat-conductive bath; means for passing a stream of said gas through said channel; a refrigerating coil immersed in said bath and means operating while said gas stream is flowing for passing a flow of refrigerating fluid through said coil to reduce the temperature of the outer of said tubes to the solidifying point of said vapor; means responsive to changes in pressure difference between the end of said channel for interrupting the flow of said refrigerating fluid when said channel becomes obstructed by said deposition of solids and for reestablishing said flow when said obstruction is removed, and means for continuously recording the temperature of said bath.

ARMOR B. MARTIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,084,987 Borchardt et al. June 29, 1937 2,229,740 Helmore Jan. 28, 1941 2,348,482 Welty May 23, 1944 FOREIGN PATENTS Number Country Date 437,434 Germany Nov. 23, 1926 875,599 France June 29, 1942 

